What this relay does and where it fits
The Siemens 3RU2126-4AB0-ZX95 is a SIRIUS thermal overload relay — size S0, CLASS 10 trip curve — designed for motor protection in control panels. It mounts directly onto the contactor (fastening method: contactor mounting) and uses a thermal bimetallic release to track motor heating. The CLASS 10 rating means it trips within 10 seconds at 7.2× the current setting, matching the acceleration profile of standard induction motors driving pumps, fans, or conveyors. Rated voltage is 690 V; at 400 V it handles motor loads up to 7.5 kW. The auxiliary switch is integrated, so you don't need a separate side-mount block for the status signal.
Key ratings and what they mean for fit
The auxiliary contact ratings tell you what the signal side can switch: 2 A at 24 V, 2 A at 230 V, 1 A at 400 V, and 3 A at 120 V — these cover typical PLC input or relay coil loads. The main circuit is screw-type terminals (M4) accepting 2x 0.5–1.5 mm² or 2x 0.75–2.5 mm² solid/stranded. Temperature compensation is active from -40 °C to +60 °C, so the trip curve stays consistent across the panel's ambient range. Mounting position is any, which helps when the enclosure forces a horizontal or upside-down layout. Power dissipation per pole is 2.7 W — factor that into the panel heat budget.
Integration and wiring notes
Physical footprint: 45 mm wide, 85 mm tall, 85 mm deep — fits a standard S0 contactor base. The screwdriver tip required is Pozidriv PZ2, shaft diameter 5–6 mm. For the main circuit, strip length is not listed, but the terminal accepts up to 2.5 mm² stranded with ferrule. The integrated auxiliary switch eliminates one extra wiring step; just confirm the NC/NO configuration matches your PLC input logic. Storage and transport range is -55 to +80 °C; operating ambient is -40 to +70 °C — fine for most indoor panel environments.